Bioenergetic and hemodynamic consequences of cellular redox manipulations by 0.2 -20 mM pyruvate were compared with those due to adrenergic stress (0.7 -1.1 pM norepinephrine) using isolated working guinea-pig hearts under the conditions of normoxia, low-flow ischemia, and reperfusion. 5 mM glucose (+ 5 U/l insulin) + 5 mM lactate were the basal energy-yielding substrates. To stabilize left ventricular enddiastolic pressure, ventricular filling pressure was held at 12 cmHzO under all conditions; this preload control minimized FrankStarling effects on ventricular inotropism. Global low-flow ischemia was induced by reducing aortic pressure to levels (20 -10 cmH20) below the coronary autoregulatory reserve. Reactants of the creatine kinase, including H + and other key metabolites, were measured by enzymatic, HPLC, and polarographic techniques.In normoxic hearts, norepinephrine stimulations of inotropism, heart rate x pressure product, and oxygen consumption (MV02) were associated with a fall in the cytosolic phosphorylation potentialas judged by the creatine kinase equilibrium. In contrast, infusion of excess pyruvate ( 5 mM) markedly increased . [Pi]) ratio at constant (normoxia) or increased (reperfusion) MVO2. In postischemic hearts the effect of pyruvate required the presence of glucose. It is proposed that pyruvate energization may improve ion pumping by the sarcoplasmic reticulum and hence Ca2+-handling by the latter which, in turn, might increase the contractile state; decreased intracellular [Pi] due to improved phosphate fixation may also be contributory. In addition, augmented pyruvate dehydrogenase flux during reperfusion seemed to expedite cellular reenergization and functional recovery in the postischemic hearts.Correspondence to R. Biinger, Department of Physiology, F. E. Hebert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814-4799, USA Abbreviations. Kcpk, Kldhr Kgapdh, Kpgkr equilibrium constant of creatine kinase, lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, and 3-phosphoglycerate kinase, respectively; pH,, intracellular pH; MV02, myocardial oxygen uptake; dy, mean hydrostatic pressure gradient across left ventricle; HR . dp, product of spontaneous heart rate and pressure; C{CrP + Cr}, total myocardial content of creatine phosphate plus creatine; Gro-3-P, sn-glycerol 3-phosphate; {ATP}, total myocardial ATP content and [ATP], mean intracellular ATP concentration (similarly for other metabolites).

Background Magnetic resonance (MR) techniques using hyperpolarized 13C have successfully produced examples of angiography and intermediary metabolic imaging, but to date no receptor imaging has been attempted. The goal of this study is to synthesize and evaluate a novel hyperpolarizable molecule, tetrafluoropropyl 1-13C-propionate-d3 (TFPP), for detecting atheromatous plaque in vivo. TFPP binds to lipid bilayers and its use in hyperpolarized MR could prove to be a major step towards receptor imaging. Results The precursor, Tetrafluoropropyl 1-13C-acrylate (TFPA) binds to dimyristoylphosphatidylcholine (DMPC) lipid bilayers with a 1.6 ppm chemical shift in the 19F MR spectrum. This molecule was designed to be hyperpolarized through addition of parahydrogen to 13C acrylate moiety by Parahydrogen Induced Polarization (PHIP). 13C TFPA was hyperpolarized to Tetrafluoropropyl 1-13C-propionate (TFPP) to a similar extent to that of hydroxyethylacrylate (HEA) to hydroxyethylpropionate (HEP); 17% +/− 4 % for TFPP vs 20% for HEP; T1 relaxation times (45s ± 2 vs 55s ± 2) were comparable and the hyperpolarized properties of TFPP were characterized. HEA, like TFPA has a chemical structure with an acrylate moiety but do not have the lipid binding Tetrafluoropropyl functional group. Hyperpolarized 13C TFPP binds to lipid bilayer appearing as a second, chemically shifted 13C hyperpolarized MR resonance with further reduction in longitudinal relaxation time (T1 = 21s ± 1). In aortas harvested from Low Density Lipoprotein Receptor (LDLR) knock-out mice fed with a high fat diet for nine months, and in which atheroma is deposited in aorta and heart, 13C TFPP showed greater binding to lipid on the intimal surface than in normal diet control mice. When 13C TFPP was hyperpolarized and administered in vivo to atheromatous mice in a pilot study, increased binding was observed on the endocardial surface of the intact heart compared to normal fed controls. Conclusions Hyperpolarized 13C TFPP has bio-sensing specificity for lipid, coupled with 42,000 fold sensitivity gain in MR signal at 4.7 Tesla. Binding of TFPP with lipids results in the formation of a characteristic second peak in MR spectroscopy. TFPP therefore has the potential to act as an in vivo molecular probe for atheromatous plaque imaging and may serve as a model of receptor targeted bioimaging with enhanced MR sensitivity.

-induced complement activation and related cardiopulmonary distress in pigs: factors promoting reactogenicity of Doxil and AmBisome" (2011).

Intravenous injection of liposomes can cause significant pulmonary hypertension in pigs, a vasoconstrictive response that provides a sensitive model for the cardiopulmonary distress in humans caused by some liposomal drugs. The reaction was recently shown to be a manifestation of "complement activation-related pseudoallergy" (CARPA; Szebeni J, Fontana JL, Wassef NM, Mongan PD, Morse DS, Dobbins DE, Stahl GL, Bünger R, and Alving CR. Circulation 99: 2302-2309, 1999). In the present study we demonstrate that the composition, size, and administration method of liposomes have significant influence on pulmonary vasoactivity, which varied between instantaneously lethal (following bolus injection of 5 mg lipid) to nondetectable (despite infusion of a 2,000-fold higher dose). Experimental conditions augmenting the pulmonary hypertensive response included the presence of dimyristoyl phosphatidylglycerol, 71 mol% cholesterol, distearoyl phosphatidylcholine, and hemoglobin in liposomes, increased vesicle size and polydispersity, and bolus injection vs. slow infusion. The vasoactivity of large multilamellar liposomes was reproduced with human C3a, C5a, and xenoreactive immunoglobulins, and it correlated with the complement activating and natural antibody binding potential of vesicles. Unilamellar, monodisperse liposomes with 0.19 +/- 0.10 microm mean diameter had no significant vasoactivity. These data indicate that liposome-induced pulmonary hypertension in pigs is multifactorial, it is due to natural antibody-triggered classic pathway complement activation and it can be prevented by appropriate tailoring of the structure and administration method of vesicles.

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